Automatic operation vehicle

ABSTRACT

An automatic operation vehicle that automatically performs an operation in an operation area is provided. A survey unit acquires the position information of the marker using a first angle between the moving direction and a direction to the marker from a first point through which the vehicle passes during the movement in a constant moving direction, a second angle between the moving direction and a direction to the marker from a second different point through which the vehicle passes during the movement in the moving direction, and a distance between the first point and the second point. The survey unit determines the first point and/or the second point during the movement of the vehicle in the moving direction such that the angle difference between the first angle and the second angle becomes close to 90°.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2016-055478, filed on Mar. 18,2016, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an automatic operation vehicle. Thepresent invention particularly relates to an automatic operation vehiclecapable of reducing the labor of a user in setting an operation area inwhich the automatic operation vehicle performs an operation.

Description of the Related Art

There is conventionally proposed an automatic operation vehicle that isequipped with an operation device such as a mowing blade and actuatesthe operation device while automatically traveling in a set operationarea. The operation area in which the automatic operation vehicleautomatically travels is set by, for example, placing a physical barriersuch as a wire by a user. For this reason, if the automatic operationvehicle contacts the physical barrier, it changes the direction by, forexample, turning not to travel outside the operation area.

To set the operation area by the physical barrier, the user needs toplace the physical barrier such as a wire throughout the boundarybetween the inside and the outside of the operation area to a height tocontact the automatic operation vehicle. U.S. Patent ApplicationPublication No. 2015/0271991 discloses a robot mower (automaticoperation vehicle) that need not a physical barrier and can store theposition information of the boundary between the inside and the outsideof an operation area.

This automatic operation vehicle is provided with a handle grippable bya user. The user can grip the handle and guide the traveling of theautomatic operation vehicle. While the user is guiding the traveling ofthe automatic operation vehicle along the boundary between the insideand the outside of an operation area, the automatic operation vehicleacquires and stores the current position of its own, thereby storing theposition of the boundary.

After storing the boundary between the inside and the outside of theoperation area, the automatic operation vehicle compares the currentposition of its own with the position of the boundary between the insideand the outside of the operation area, thereby implementing travelingonly in the operation area. Hence, for this automatic operation vehicle,the user need not place a physical barrier such as a wire throughout theboundary between the inside and the outside of the operation area.

However, to set the operation area for the automatic operation vehicle,the user needs to guide the traveling of the automatic operation vehiclealong the boundary between the inside and the outside of the operationarea. For this reason, the present inventors recognized that there isroom for improvement of an existing automatic operation vehicle toreduce the labor of a user in setting an operation area.

SUMMARY OF THE INVENTION

An aspect of the present invention provides an automatic operationvehicle capable of reducing the labor of a user in setting an operationarea in which the automatic operation vehicle performs an operation.Other aspects of the present invention will be apparent to those skilledin the art by referring to embodiments to be described below and theaccompanying drawings.

According to some embodiments of the present invention, an automaticoperation vehicle that automatically performs an operation in anoperation area is provided. The vehicle includes a behavior acquisitionunit configured to acquire behavior information including a distance ofa movement of the automatic operation vehicle and a direction of themovement; an image analysis unit configured to extract a marker includedin an image captured by a camera provided on the automatic operationvehicle; and a survey unit configured to acquire, by triangulation,position information of the marker extracted by the image analysis unit.The survey unit acquires the position information of the marker using afirst angle that is an angle difference between the moving direction anda direction to the marker from a first point through which the automaticoperation vehicle passes during the movement in a constant movingdirection, a second angle that is an angle difference between the movingdirection and a direction to the marker from a second point throughwhich the automatic operation vehicle passes during the movement in themoving direction, and a distance between the first point and the secondpoint, the second point being different from the first point. The surveyunit determines the first point and/or the second point during themovement of the automatic operation vehicle in the moving direction suchthat the angle difference between the first angle and the second anglebecomes close to 90°.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments (with reference to theattached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view showing an example of the overall arrangement ofan automatic operation vehicle according to some embodiments of thepresent invention;

FIG. 2 is a plan view of the automatic operation vehicle shown in FIG.1;

FIG. 3 is a block diagram showing an example of the arrangement of acircuit board shown in FIG. 1 and devices connected to the circuitboard;

FIG. 4 is a block diagram showing an example of the arrangement of anelectronic control unit shown in FIG. 3;

FIG. 5 is a view showing an example of the operation area of theautomatic operation vehicle shown in FIG. 1;

FIG. 6 is a view for explaining the principle of triangulation by asurvey unit shown in FIG. 4;

FIG. 7 is a view showing an example of the movement of the automaticoperation vehicle shown in FIG. 1 when acquiring the positioninformation of a plurality of markers;

FIG. 8 is a flowchart showing an example of the operation of theautomatic operation vehicle shown in FIG. 1 when acquiring the positioninformation of the markers;

FIG. 9 is a view for explaining an error that occurs when a cameracaptures a marker;

FIGS. 10A and 10B are views for explaining the accuracy of a survey bythe survey unit shown in FIG. 4 considering an error that occurs whenthe camera captures a marker;

FIGS. 11A and 11B are views for explaining the accuracy of a survey bythe survey unit shown in FIG. 4 considering an error that occurs whenthe camera captures a marker;

FIG. 12 is a flowchart showing an example of a detailed process of thestep of acquiring the position information of the markers in theflowchart of FIG. 8;

FIG. 13 is a view showing an example in which the automatic operationvehicle moves in a constant direction if an obstacle exists between amarker and the automatic operation vehicle shown in FIG. 1; and

FIGS. 14A to 14D are views showing an example of image analysis by animage analysis unit shown in FIG. 4 in the state shown in FIG. 13.

DESCRIPTION OF THE EMBODIMENTS

Embodiments to be described below are used to easily understand thepresent invention. Hence, those skilled in the art should remember thatthe present invention is not improperly limited by the embodiments to beexplained below.

<<1. Arrangement Example of Automatic Operation Vehicle>>

An example of the overall arrangement of an automatic operation vehicle10 will be described with reference to FIGS. 1 and 2. The automaticoperation vehicle 10 will also be referred to as the operation vehicle10 hereinafter. As an example of the operation vehicle 10, FIG. 1 showsa robot mower capable of autonomously traveling to mow a lawn. Theoperation vehicle 10 includes a housing 11, left and right front wheels12 provided on the front side of the housing 11, left and right rearwheels 13 provided on the rear side of the housing 11, and an operationunit 14 provided on the lower side at the center of the housing 11. Inthe example shown in FIG. 1, a mowing blade is shown as an example ofthe operation unit 14 in the case in which the operation vehicle 10 is arobot mower.

The operation vehicle 10 includes, in the housing 11, left and righttraveling motors 15 that individually drive the left and right rearwheels 13, a driving motor 16 that drives the operation unit 14, abattery 17, a wheel speed sensor 18, and a circuit board 30 on which anECU (Electronic Control Unit) 31, an angular velocity sensor 32, and anacceleration sensor 33 are mounted. The operation vehicle 10 also has,on the housing 11, a camera 21 capable of capturing the outside of theoperation vehicle 10. The camera 21 includes, for example, an imagesensor such as a CCD or CMOS sensor and an imaging lens configured toform an image of an object on the imaging plane of the image sensor, andcan generate an image of a digital format.

The traveling motors 15, the driving motor 16, the wheel speed sensor18, the ECU 31, the angular velocity sensor 32, the acceleration sensor33, and the camera 21 receive power supplied from the battery 17. Forexample, the traveling motors 15, the driving motor 16, the wheel speedsensor 18, the angular velocity sensor 32, the acceleration sensor 33,and the camera 21 may receive power supplied from the battery 17 via theECU 31.

The ECU 31 receives signals (or data) from the wheel speed sensor 18,the angular velocity sensor 32, the acceleration sensor 33, and thecamera 21 and controls the operations of the traveling motors 15 and thedriving motor 16. The ECU 31 individually controls the left and righttraveling motors 15, thereby controlling the movement of the operationvehicle 10.

That is, as shown in FIG. 2, the left traveling motor 15 individuallydrives the left rear wheel 13, and the right traveling motor 15individually drives the right rear wheel 13. For example, when both theleft and right traveling motors 15 rotate in the forward direction at auniform velocity, the operation vehicle 10 travels straight forward(moves ahead). Similarly, when both the left and right traveling motors15 rotate in the reverse direction at a uniform velocity, the operationvehicle 10 travels straight backward (moves back).

If the traveling motor 15 on the left side and the traveling motor 15 onthe right side rotate in the forward direction at different velocities,the operation vehicle 10 turns in the direction of the motor with thelower rotation speed out of the left and right traveling motors 15. Ifone of the left and right traveling motors 15 rotates in the forwarddirection, and the other rotates in the reverse direction at the samerotation speed, the operation vehicle 10 can turn in the direction ofthe reversely rotating motor out of the left and right traveling motors15 without changing the position of the operation vehicle 10.

An example of the arrangement of the circuit board 30 and the devicesconnected to the circuit board 30 will be described with reference toFIG. 3. As shown in FIG. 3, the circuit board 30 includes the ECU 31,the angular velocity sensor 32, the acceleration sensor 33, a driver 36that individually controls the rotations of the left and right travelingmotors 15, and a driver 37 that controls the rotation of the drivingmotor 16. The circuit board 30 is electrically connected to the camera21, the battery 17, and the wheel speed sensor 18.

The angular velocity sensor 32 outputs, to the ECU 31, a signalrepresenting a yaw rate that is the turning angle velocity of thebarycentric position (not shown) of the operation vehicle 10 about avertical axis. That is, the ECU 31 receives the signal representing theyaw rate from the angular velocity sensor 32, thereby acquiring thefront direction (traveling direction) of the operation vehicle 10 by acalculation or the like.

The acceleration sensor 33 outputs, to the ECU 31, a signal representingan acceleration acting in, for example, three directions, that is, thefront-and-rear direction, the left-and-right direction, and the verticaldirection of the operation vehicle 10. The acceleration sensor 33 neednot always output a signal representing the acceleration acting in thethree directions, and may output a signal representing an accelerationacting in, for example, one or two of the three directions.

The driver 36 individually controls the rotations of the left and righttraveling motors 15 in accordance with a signal received from the ECU31. The driver 37 controls the rotation of the driving motor 16 inaccordance with a signal received from the ECU 31. In the example shownin FIG. 3, the angular velocity sensor 32, the acceleration sensor 33,the driver 36, and the driver 37 are provided on the circuit board 30 asconstituent elements separated from the ECU 31. However, for example,the ECU 31 may include at least one of them.

The wheel speed sensor 18 is provided in the operation vehicle 10 to beable to detect the rotation speed of the rear wheels 13, and outputs asignal representing the rotation speed of the rear wheels 13 to thecircuit board 30, more specifically, the ECU 31. That is, the ECU 31receives the signal representing the rotation speed of the rear wheels13 from the wheel speed sensor 18, thereby acquiring the distance of themovement of the operation vehicle 10 by a calculation or the like.

The camera 21 is provided on the operation vehicle 10 to be able tocapture the outside of the operation vehicle 10, and outputs the data ofa captured image to the circuit board 30, more specifically, the ECU 31.In the example shown in FIG. 3, one camera 21 is electrically connectedto the circuit board 30. However, two or more cameras 21 may beconnected to the circuit board 30.

Cameras 21 in an appropriate number may be provided at appropriatepositions on the operation vehicle 10 so as to capture the wholecircumference of the operation vehicle 10. For example, a total of fourcameras 21 may be provided such that one camera 21 is arranged on eachof the front, rear, left, and right sides of the housing 11 of theoperation vehicle 10. Alternatively, for example, one camera 21 havingan angle of view capable of capturing the whole circumference of theoperation vehicle 10 may be provided on the upper portion of the housing11 of the operation vehicle 10.

An example of the arrangement of the ECU 31 will be described withreference to FIG. 4. The ECU 31 is formed from, for example, amicrocomputer including a processing unit 40 such as a CPU (CentralProcessing Unit), and a storage unit 50 such as a RAM (Random AccessMemory) and a ROM (Read Only Memory). The storage unit 50 stores mapdata (map) 51 concerning an operation area that is a range where theoperation vehicle 10 performs an operation.

The processing unit 40, for example, executes a program (not shown)stored in the storage unit 50, thereby functioning as a moving directiondetermination unit 41, an image analysis unit 43, a behavior acquisitionunit 44, and a survey unit 45. Alternatively, at least one of the movingdirection determination unit 41, the image analysis unit 43, thebehavior acquisition unit 44, or the survey unit 45 may be implementedby, for example, hardware such as an analog circuit.

The moving direction determination unit 41 determines the direction(moving direction) to move the operation vehicle 10. The image analysisunit 43 receives an image obtained by capturing the outside of theoperation vehicle 10 by the camera 21, and analyzes the image using, forexample, known image processing and pattern matching methods. If theoperation vehicle 10 includes a plurality of cameras 21, the imageanalysis unit 43 may analyze an image of the whole circumference of theoperation vehicle 10, which is obtained by connecting captured images ofthe outside of the operation vehicle 10 received from the plurality ofcameras 21. If the received image includes a marker (to be describedlater), the image analysis unit 43 extracts the marker. The imageanalysis unit 43 acquires the angle difference between the frontdirection (traveling direction) of the operation vehicle 10 and adirection indicating a marker extracted from the current position of theoperation vehicle 10 by a calculation or the like.

The behavior acquisition unit 44 acquires behavior information includingthe distance and direction of the movement of the operation vehicle 10.The behavior acquisition unit 44 acquires the distance of the movementof the operation vehicle 10 in accordance with a signal received fromthe wheel speed sensor 18 by a calculation or the like. The behavioracquisition unit 44 also acquires the direction of the movement of theoperation vehicle 10 in accordance with a signal received from theangular velocity sensor 32 by a calculation or the like. The behavioracquisition unit 44 may further include, in the behavior information,for example, information acquired according to a signal received fromthe acceleration sensor 33 by a calculation or the like.

The survey unit 45 acquires the position information of a markerextracted by the image analysis unit 43 by triangulation (to bedescribed later) using the analysis result of the image analysis unit 43and the behavior information obtained by the behavior acquisition unit44. The survey unit 45, for example, reflects the obtained positioninformation of the marker on the map 51.

As operation modes of the operation vehicle 10, the operation vehicle 10has, for example, an operation mode and a survey mode. When operating inthe operation mode, the operation vehicle 10 autonomously travels in theoperation area and performs an operation of, for example, mowing a lawn.When operating in the survey mode, the operation vehicle 10 acquires theposition information of a marker and updates the map 51 duringautonomous traveling.

<<2. Example of Operation of Automatic Operation Vehicle>>

<<2-1. Relationship Between Operation Area and Operation of AutomaticOperation Vehicle>>

The relationship between an operation area 70 and the operation of theoperation vehicle 10 will be described with reference to FIG. 5. FIG. 5shows an example in which the operation area 70 is viewed from above. Inthe example shown in FIG. 5, the operation area 70 is represented by arange surrounded by a broken line. In the example shown in FIG. 5, astation 60 capable of storing the operation vehicle 10 is illustrated.When stored in the station 60, the operation vehicle 10 can charge thebattery 17. When the operation in the operation mode or the survey modeends, the operation vehicle 10 may move to the station 60 and be stored.Note that in the example shown in FIG. 5, the station 60 is arrangedacross the boundary between the inside and the outside of the operationarea 70. However, the station 60 may be arranged inside the operationarea 70 or outside the operation area 70.

The operation vehicle 10 can set (or store) the operation area 70 on themap 51 stored in the storage unit 50 of the ECU 31. The map 51 is, forexample, a two-dimensional map representing the same plane as theground. Position information (two-dimensional coordinates) on the map 51and position information (two-dimensional coordinates) on the real spacehave a correspondence relationship. The position information(two-dimensional coordinates) on the real space is represented by acoordinate plane on the same plane as the ground. The coordinate planehas its origin at a preset position or the position where the station 60is arranged, and includes two coordinate axes, that is, an X-axis and aY-axis intersecting the X-axis at a right angle. Note that in theexample shown in FIG. 5, the origin and the X- and Y-axes are notillustrated, and an example in the X-axis positive direction and theY-axis positive direction is shown.

In the example shown in FIG. 5, the rectangular operation area 70 isshown. Markers 71 (71-1, 71-2, 71-3, and 71-4) exist at the four apexesof the rectangle. That is, in the example shown in FIG. 5, the rangeinside a rectangle defined by four coordinate points corresponding tothe positions of the four markers 71 (71-1, 71-2, 71-3, and 71-4) on thereal space is set as the operation area 70 on the map 51.

As described above, the operation vehicle 10 can acquire, by thebehavior acquisition unit 44 of the ECU 31, behavior informationincluding the distance of the movement of the operation vehicle 10 andthe direction of the movement of the operation vehicle 10. For thisreason, the operation vehicle 10 can grasp the current position of theoperation vehicle 10 on the map 51.

After setting the operation area 70 on the map 51 in this way, theoperation vehicle 10 can travel only inside the operation area 70. As aresult, when, for example, operating in the operation mode, theoperation vehicle 10 can implement autonomously traveling only insidethe operation area 70 and performing an operation of, for example,mowing a lawn.

To set the operation area 70 on the map 51, position information(two-dimensional coordinates) concerning the boundary between the insideand the outside of the operation area 70 on the real space needs to begrasped. In the operation vehicle 10, the survey unit 45 acquires theposition information (two-dimensional coordinates) of each marker 71 onthe real space by triangulation as the position information concerningthe boundary between the inside and the outside of the operation area70. Note that the user can edit the map 51. For example, a positionspaced apart from the position information of the marker 71 reflected onthe map 51 by an arbitrary distance may be set on the boundary betweenthe inside and the outside of the operation area 70.

The marker 71 is an object that the image analysis unit 43 can extractfrom an image received from the camera 21, and may be, for example, arod-shaped object capable of standing on the ground. A tree, a stone, orthe like may be used as the marker 71 as long as the image analysis unit43 can extract it from the image received from the camera 21. Inaddition, the marker 71 may be, for example, configured to be able toemit light in a specific frequency domain to be captured by the camera21.

<<2-2. Acquisition of Position Information of Marker by Triangulation>>

An example of a method of acquiring the position information(two-dimensional coordinates) of the marker 71 using triangulation bythe survey unit 45 will be described with reference to FIG. 6. FIG. 6shows an example in which the operation vehicle 10 that moves in aconstant direction and the marker 71 are viewed from above.

Let L be the distance between a position 10-A and a position 10-B,through which the operation vehicle 10 moving in the constant directionpasses. Let HA be the distance of a line that connects the position 10-Aand the position of the marker 71. Let θA be the angle made by thedirection of the movement of the operation vehicle 10 and the line thatconnects the position 10-A and the position of the marker 71. Let θB bethe angle made by the direction of the movement of the operation vehicle10 and a line that connects the position 10-B and the position of themarker 71. Let θα be the angle made by the line that passes through theposition 10-A and the position of the marker 71 and the line that passesthrough the position 10-B and the position of the marker 71. At thistime, based on the sine theorem, we obtain

HA/sin(π−θB)=L/sin θα

HA/sin θB=L/sin(θB−θA)

(∵ sin(π−θB)=sin θB, θα=θB−θA)  (1)

In addition, equations (1) can be rewritten as

HA=L·sin θB/sin(θB−θA)  (2)

When L, θA, and θB are thus obtained, HA can be determined bycalculating equation (2). Here, the survey unit 45 can obtain L, θA, andθB as the operation vehicle 10 moves in the constant direction from theposition 10-A to the position 10-B. That is, L is acquired by thebehavior acquisition unit 44, and OA and θB are acquired by the imageanalysis unit 43. Hence, the survey unit 45 can acquire informationrepresenting that the marker 71 is arranged at a position spaced partfrom the position 10-A by HA in a direction with the angle difference θAwith respect to the front direction (traveling direction) of theoperation vehicle 10 at the position 10-A. In the above-described way,the survey unit 45 acquires the position information (two-dimensionalcoordinates) of the marker 71.

Of two positions (corresponding to the positions 10-A and 10-B in FIG.6) that the operation vehicle 10 passes through during a movement in aconstant direction when the survey unit 45 acquires the positioninformation of the marker 71 using triangulation, one will also bereferred to as a first point (corresponding to the position 10-A in FIG.6), and the other will also be referred to as a second point(corresponding to the position 10-B in FIG. 6). In addition, the angledifference between the moving direction and the direction from the firstpoint to the marker 71 will also be referred to as a first angle(corresponding to the angle θA in FIG. 6), and the angle differencebetween the moving direction and the direction from the second point tothe marker 71 will also be referred to as a second angle (correspondingto the angle θB in FIG. 6).

<<2-3. Example of Operation of Automatic Operation Vehicle in SurveyMode>>

An example of the operation of the operation vehicle 10 in the surveymode will be described with reference to FIGS. 7 and 8. FIG. 7 shows anexample in which the operation vehicle 10 and the four markers 71 (71-1,71-2, 71-3, and 71-4) are viewed from above. In the example shown inFIG. 7, the operation vehicle 10 is assumed to start the survey mode ata position 10-1.

The operation vehicle 10 that has started execution of the survey modecaptures the outside of the operation vehicle 10 by the camera 21 at theposition 10-1. The image analysis unit 43 receives the image captured bythe camera 21 and analyzes it. If the marker 71-1 is included in theanalyzed image, the image analysis unit 43 extracts the marker 71-1. Thesurvey unit 45 starts acquiring the position information of the marker71-1 extracted by the image analysis unit 43.

For the marker 71-1 for which the survey unit 45 starts acquiring theposition information, the moving direction determination unit 41determines the moving direction in which the operation vehicle 10 movesto acquire the position information. That is, the moving directiondetermination unit 41 determines, as the moving direction of theoperation vehicle 10, a direction in which the operation vehicle 10 doesnot come into contact with the marker 71 (marker 71-1), and an angledifference θg (θg1) with respect to the direction from the currentposition (position 10-1) of the operation vehicle 10 to the marker 71(marker 71-1) is smaller than 90°.

When the moving direction determination unit 41 determines the movingdirection of the operation vehicle 10, the operation vehicle 10 turnsuntil the front direction (traveling direction) matches the movingdirection determined by the moving direction determination unit 41.After the front direction (traveling direction) matches the movingdirection determined by the moving direction determination unit 41, theoperation vehicle 10 moves (moves ahead) in the front direction(traveling direction). During the movement of the operation vehicle 10,the survey unit 45 acquires the position information of the marker 71(marker 71-1) by the above-described triangulation.

As described above, when the survey unit 45 starts acquiring theposition information of the marker 71, the moving directiondetermination unit 41 determines the moving direction of the operationvehicle 10. This makes it possible to acquire the position informationof the marker 71 without causing the user to acquire the positioninformation of the marker 71 by himself/herself and guide the movingdirection of the operation vehicle 10. In addition, since the movingdirection determined by the moving direction determination unit 41 is adirection in which the operation vehicle 10 does not come into contactwith the marker 71, and the angle difference θg with respect to thedirection from the current position of the operation vehicle 10 to themarker 71 is smaller than 90°, a timing is generated at which thedistance between the operation vehicle 10 and the marker 71 shortensduring the movement of the operation vehicle 10 in the determined movingdirection. That is, as compared to a case in which the operation vehicle10 moves in a direction in which the angle difference θg with respect tothe direction from the current position of the operation vehicle 10 tothe marker 71 is 90° or more, and the timing at which the distancebetween the operation vehicle 10 and the marker 71 shortens is notgenerated, the position information of the marker 71 can be acquiredbased on an image captured when the distance to the marker 71 is short.

The moving direction determined by the moving direction determinationunit 41 may be a direction in which the operation vehicle 10 does notcome into contact with the marker 71, and the angle difference θg withrespect to the direction from the current position of the operationvehicle 10 to the marker 71 is smaller than 45°. In this case, thetiming at which the distance between the operation vehicle 10 and themarker 71 shortens is sufficiently generated during the movement of theoperation vehicle 10 in the determined moving direction.

The survey unit 45 may determine whether acquisition of the positioninformation of the marker 71 (marker 71-1) extracted by the imageanalysis unit 43 is completed. Upon determining that acquisition of theposition information of the marker 71 (marker 71-1) is not completed,the survey unit 45 may start acquiring the position information of themarker 71 (marker 71-1). For example, the survey unit 45 may refer tothe map 51 and determine the marker 71 with stored position informationas the marker 71 for which the position information acquisition iscompleted. Alternatively, the survey unit 45 may determine the marker 71for which the position information acquisition was executed apredetermined number of times as the marker 71 for which the positioninformation acquisition is completed.

When the survey unit 45 starts acquiring the position information of themarker 71 for which the position information acquisition is notcompleted, the position information acquisition can be prevented frombeing executed again for the marker 71 for which the positioninformation acquisition is already completed. As a result, for example,the power consumption of the battery 17 for the operation in the surveymode can be reduced.

If the received image includes a plurality of markers 71, the imageanalysis unit 43 extracts all the markers 71. The survey unit 45determines whether the plurality of markers 71 extracted by the imageanalysis unit 43 include the marker 71 for which the positioninformation acquisition is not completed. If the marker 71 for which theposition information acquisition is not completed is included, thesurvey unit 45 starts acquiring the position information of the marker71 of the highest visibility from the current position of the operationvehicle 10 out of the markers 71 for which the position informationacquisition is not completed. The marker 71 of the highest visibilityfrom the current position of the operation vehicle 10 may be, forexample, the marker 71 whose size on the received image is largest. Forexample, the same procedure as described above is repeated until themarker 71 for which the position information acquisition is notcompleted is not included any more in the image captured by the camera21 at the position where the acquisition of the position information ofthe marker 71 is completed.

More specifically, in the example shown in FIG. 7, assume that an imagecaptured by the camera 21 when the operation vehicle 10 is located atthe position 10-1 includes the four markers 71 (71-1, 71-2, 71-3, and71-4) for which the position information acquisition is not completed.At this time, the image analysis unit 43 extracts the four markers 71(71-1, 71-2, 71-3, and 71-4) included in the received image, and thesurvey unit 45 determines that the acquisition of the positioninformation of the four markers 71 (71-1, 71-2, 71-3, and 71-4) is notcompleted. The survey unit 45 starts acquiring the position informationof the marker 71-1 of the highest visibility from the current position(position 10-1) of the operation vehicle 10 out of the four markers 71(71-1, 71-2, 71-3, and 71-4) for which the position informationacquisition is not completed. Then, the moving direction determinationunit 41 determines the moving direction of the operation vehicle 10.While the operation vehicle 10 is moving in the determined movingdirection, the survey unit 45 acquires the position information of themarker 71-1.

After that, assume that an image captured by the camera 21 at a position(for example, a position 10-2) where the acquisition of the positioninformation of the marker 71-1 is completed includes the four markers 71(71-1, 71-2, 71-3, and 71-4). At this time, the image analysis unit 43extracts the four markers 71 (71-1, 71-2, 71-3, and 71-4) included inthe received image, and the survey unit 45 determines that theacquisition of the position information of the three markers 71 (71-2,71-3, and 71-4) is not completed. The survey unit 45 starts acquiringthe position information of the marker 71-2 of the highest visibilityfrom the current position (position 10-2) of the operation vehicle 10out of the three markers 71 (71-2, 71-3, and 71-4) for which theposition information acquisition is not completed.

At a position (for example, a position 10-3) where the acquisition ofthe position information of the marker 71-2 is completed, acquisition ofthe position information of the marker 71-3 is started in accordancewith the same procedure as described above. In addition, at a position(for example, a position 10-4) where the acquisition of the positioninformation of the marker 71-3 is completed, acquisition of the positioninformation of the marker 71-4 is started in accordance with the sameprocedure as described above. When starting the position informationacquisition for any marker 71, the moving direction determined by themoving direction determination unit 41 is a direction in which theoperation vehicle 10 does not come into contact with the marker 71, andthe angle difference θg (θg1, θg2, θg3, or θg4) with respect to thedirection from the current position of the operation vehicle 10 to themarker 71 is smaller than 90°.

If the survey unit 45 determines that an image captured by the camera 21at a position (not shown) where the acquisition of the positioninformation of the marker 71-4 is completed includes no marker 71 forwhich the position information acquisition is not completed, theoperation vehicle 10 may end the operation in the survey mode. However,alternatively, for example, if the acquisition of the positioninformation of all markers 71 is completed three times, the operationvehicle 10 may end the operation in the survey mode.

As described above, when an image captured by the camera 21 includes theplurality of markers 71, the survey unit 45 determines the marker 71whose position information is to be acquired. Hence, the user need notdetermine the marker 71 whose position information is to be acquired. Inaddition, the survey unit 45 starts acquiring the position informationof the marker 71 of the highest visibility from the current position ofthe operation vehicle 10 out of the markers 71 for which the positioninformation acquisition is not completed. For example, as compared to acase in which the acquisition of the position information of the marker71 farthest from the current position of the operation vehicle 10 isstarted, the moving distance needed until the position informationacquisition is completed for all markers 71 is shortened. As a result,the power consumption of the battery 17 for the operation in the surveymode can be reduced.

An example of a series of procedures of the operation of the operationvehicle 10 in the survey mode will be described with reference to theflowchart of FIG. 8. In step S101, the camera 21 of the operationvehicle 10 captures the outside of the operation vehicle 10. In stepS102, the image analysis unit 43 analyzes the image captured by thecamera 21 and extracts the markers 71 included in the image. In stepS103, the survey unit 45 determines whether the markers 71 extracted bythe image analysis unit 43 include the marker 71 for which the positioninformation acquisition is not completed.

If YES in step S103, the process advances to step S104. If NO in stepS103, the procedure ends. In step S104, the survey unit 45 determinesthe marker 71 whose position information is to be acquired, and themoving direction determination unit 41 determines the moving directionof the operation vehicle 10. In step S105, the operation vehicle 10starts moving in the moving direction determined by the moving directiondetermination unit 41, and during the movement of the operation vehicle10 in the moving direction, the survey unit 45 acquires the positioninformation of the marker 71 by the above-described triangulation.

In step S106, the survey unit 45 reflects the acquired positioninformation of the marker 71 on the map 51 and updates the map 51. Whenthe update of the map 51 ends, the process returns to step S101. Thatis, the processes of steps S101 to S106 are repeated until it isdetermined in step S103 that the markers 71 extracted by the imageanalysis unit 43 do not include the marker 71 for which the positioninformation acquisition is not completed.

<<2-4. Accuracy of Position Information Acquisition>>

The accuracy of acquisition of the position information of the marker 71by the survey unit 45 will be described with reference to FIGS. 9 to11B. FIG. 9 shows an example in which the operation vehicle 10 and themarker 71 are viewed from above. In the example shown in FIG. 9, theoperation vehicle 10 and the marker 71 are spaced apart by a distance H.

Generally, in a camera capable of generating an image of a digitalformat, when forming an image of an object on the imaging plane of animage sensor, an error occurs because of the resolution of the imagesensor, the focal length of the imaging lens, and the like. Under theinfluence of this error, an imaging error ±θp (the range of the imagingerror is 2θp) of a predetermined angle occurs when the camera 21captures an image. When the imaging error ±θp occurs, the marker 71spaced apart from the operation vehicle 10 by the distance H is capturedwhile including an error in the range of 2H tan θp on the real space.That is, the influence of the imaging error becomes large as thedistance between the camera 21 and the marker 71 increases.

The influence of the imaging error in acquiring the position informationof the marker 71 by triangulation will be described with reference toFIGS. 10A to 11B. A region 76 shown in FIGS. 10A and 10B represents therange of an error in acquiring the position information of the marker 71using triangulation. The region 76 is a region formed by the overlap ofan imaging error generated when capturing the marker 71 at a position Athat is an example of the first point and an imaging error generatedwhen capturing the marker 71 at a position B that is an example of thesecond point.

In the example shown in FIG. 10A and the example shown in FIG. 10B, thedistance from the position A (first point) to the marker 71 and thedistance from the position B (second point) to the marker 71 almostequal. However, the region 76 is smaller in FIG. 10B in which the anglemade by the position A (first point), the marker 71, and the position B(second point) is close to 90° than in FIG. 10A. Note that the anglemade by the position A (first point), the marker 71, and the position B(second point) is the same as the angle difference between the firstangle and the second angle.

As described above, when the imaging error is taken into consideration,the accuracy of the acquisition of the position information of themarker 71 improves as the angle difference between the first angle andthe second angle used in the triangulation becomes close to 90°. Thatis, the survey unit 45 determines the first point and/or the secondpoint during the movement of the operation vehicle 10 in the movingdirection such that the angle difference between the first angle and thesecond angle becomes close to 90°, thereby reducing the imaging error.As a result, the user need not determine the first point and the secondpoint to guarantee the accuracy of the acquisition of the positioninformation of the marker 71.

FIGS. 11A and 11B show two examples representing the accuracy of theacquisition of the position information of the marker 71 usingtriangulation in a case in which the angle difference between the firstangle and the second angle is about 90°. The region 76 in FIG. 11A islarger than the region 76 in FIG. 11B. This is because the distance fromthe position A (first point) to the marker 71 in FIG. 11A is longer thanthe distance from the position A (first point) to the marker 71 in FIG.11B, and therefore, the imaging error has a large influence.

In the case in which the angle difference between the first angle andthe second angle is about 90°, both the distance between the first pointand the marker 71 and the distance between the second point and themarker 71 are shortest under the condition that the first angle θA ofabout 45° and the second angle θB of about 135° hold, as shown in FIG.11B. That is, during the movement of the operation vehicle 10 in themoving direction, the survey unit 45 determines the first point suchthat the first angle becomes close to 45° and also determines the secondpoint such that the second angle becomes close to 135°, therebyimproving the accuracy of the acquisition of the position information ofthe marker 71.

From the viewpoint of the accuracy of the acquisition of the positioninformation of the marker 71 as well, the moving direction determined bythe moving direction determination unit 41 when the survey unit 45starts acquiring the position information of the marker 71 may be adirection in which the operation vehicle 10 does not come into contactwith the marker 71, and the angle difference θg with respect to thedirection from the current position of the operation vehicle 10 to themarker 71 is smaller than 45°. That is, if the moving direction of theoperation vehicle 10 is a direction in which the angle difference θgwith respect to the direction from the current position of the operationvehicle 10 to the marker 71 is smaller than 45°, during the movement,the operation vehicle 10 always passes through the first point at whichthe first angle is 45°.

<<2-5. Processing Concerning Acquisition of Position Information ofMarker>>

An example of a detailed process of acquiring the position informationof the marker 71 by the survey unit 45 will be described with referenceto the flowchart of FIG. 12. The flowchart of FIG. 12 shows an exampleof a detailed process of step S105 in the flowchart of FIG. 8.

In step S201, the survey unit 45 determines whether a marker detectionflag is ON. If YES in step S201, the process advances to step S205. IfNO in step S201, the process advances to step S202. Note thatimmediately after the process advances from step S104 to step S105 inthe flowchart of FIG. 8, the marker detection flag is OFF.

In step S202, the survey unit 45 determines whether an image captured bythe camera 21 at the current position includes the marker 71. If YES instep S202, the process advances to step S203. If NO in step S202, theprocess returns to START.

In step S203, the survey unit 45 stores, as the first angle, the angledifference between the moving direction of the operation vehicle 10 atthe position where the image determined in step S202 was captured andthe direction from the operation vehicle 10 to the marker 71. The angledifference between the moving direction of the operation vehicle 10 atthe position where the image was captured and the direction from theoperation vehicle 10 to the marker 71 will also be referred to as amarker detection angle hereinafter. The survey unit 45 receives themarker detection angle from, for example, the image analysis unit 43. Instep S203, the survey unit 45 also stores the position where the imagedetermined in step S202 was captured as the first point. The positionwhere the image was captured will also be referred to as a markerdetection position hereinafter. The survey unit 45 receives the markerdetection position from, for example, the behavior acquisition unit 44.

In step S204, the survey unit 45 turns on the marker detection flag.When the process of step S204 ends, the process returns to START. Instep S205, the survey unit 45 determines whether the first angle isdetermined. If YES in step S205, the process advances to step S211. IfNO in step S205, the process advances to step S206.

In step S206, the survey unit 45 determines whether an image captured bythe camera 21 at the current position includes the marker 71. If YES instep S206, the process advances to step S207. If NO in step S206, theprocedure ends. Note that if step S206 ends with NO, and the procedureends, a situation in which the marker 71 that should be detectablecannot be detected due to some reason (the image analysis unit 43 cannotextract the marker 71) has occurred. Hence, the process returns to, forexample, step S101 in the flowchart of FIG. 8.

In step S207, the survey unit 45 determines whether the marker detectionangle at the position where the image determined in step S206 wascaptured is closer to 45° than the first angle. If YES in step S207, theprocess advances to step S208. If NO in step S207, the process advancesto step S209.

In step S208, the survey unit 45 stores (overwrites) the markerdetection angle at the position where the image determined in step S206was captured newly as the first angle in place of the currently storedfirst angle. In step S208, the survey unit 45 also stores (overwrites)the position where the image determined in step S206 was captured newlyas the first point in place of the currently stored first point.

In step S209, the survey unit 45 determines the currently stored firstangle and the currently stored first point as the first angle and thefirst point to be used in triangulation. In step S210, the survey unit45 stores the marker detection angle at the position where the imagedetermined in step S206 was captured as the second angle, and stores theposition where the image was captured as the second point. When theprocess of step S208 or S210 ends, the process returns to START.

By having the processes of steps S207, S208, and S209, the survey unit45 can determine the first point during the movement of the operationvehicle 10 in the moving direction such that the first angle becomesclose to 45°. As a result, the accuracy of the acquisition of theposition information of the marker 71 improves.

In step S211, the survey unit 45 determines whether an image captured bythe camera 21 at the current position includes the marker 71. If YES instep S211, the process advances to step S212. If NO in step S211, theprocess advances to step S214.

In step S212, the survey unit 45 determines whether the angle differencebetween the determined first angle and the marker detection angle at theposition where the image determined in step S211 was captured is closerto 90° than the angle difference between the determined first angle andthe currently stored second angle. If YES in step S212, the processadvances to step S213. If NO in step S212, the process advances to stepS214.

In step S213, the survey unit 45 stores the marker detection angle atthe position where the image determined in step S211 was captured newlyas the second angle in place of the currently stored second angle. Instep S213, the survey unit 45 also stores the position where the imagedetermined in step S211 was captured newly as the second point in placeof the currently stored second point. When the process of step S213ends, the process returns to START.

In step S214, the survey unit 45 determines the currently stored secondangle and the currently stored second point as the second angle and thesecond point to be used in triangulation. In step S215, the survey unit45 calculates and acquires the position information of the marker 71 bytriangulation using the determined first angle, the determined secondangle, and the distance between the determined first point and thedetermined second point. When the process of step S215 ends, theprocedure ends. That is, when the process of step S215 ends, the processadvances to step S106 in the flowchart of FIG. 8.

By having the processes of steps S212, S213, and S214, the survey unit45 can determine the second point during the movement of the operationvehicle 10 in the moving direction such that the second angle becomesclose to 135°. As a result, the accuracy of the acquisition of theposition information of the marker 71 improves.

The flowchart of FIG. 12 is merely an example, and the survey unit 45need not execute the processes of all steps. The survey unit 45 mayexecute, for example, processing for determining the first point, thatis, processing corresponding to steps S201 to S209 in the flowchart ofFIG. 12. In addition, the survey unit 45 may execute, for example,processing for determining the second point, that is, processingcorresponding to steps S211 to S215 in the flowchart of FIG. 12.

<<2-6. Operation in Special Case>>

As an example of a special case, an example of an operation performed ifa situation in which the marker 71 that should be extractable from animage captured by the camera 21 cannot be extracted by the imageanalysis unit 43 from an image captured by the camera 21 has occurredduring the movement of the operation vehicle 10 will be described withreference to FIGS. 13 to 14D. The “situation in which the marker 71 thatshould be extractable from an image captured by the camera 21 cannot beextracted by the image analysis unit 43 from an image captured by thecamera 21” will also be referred to as a lost hereinafter. The lost canoccur when, for example, a tree, a rock, or the like whose position isfixed or a human, an animal, or the like whose position is not fixedstands as an obstacle 78 between the camera 21 and the marker 71. Thelost can also occur due to, for example, backlight.

FIG. 13 shows an example in which the operation vehicle 10 that moves ina predetermined moving direction and the marker 71 are viewed fromabove. FIG. 13 also shows the obstacle 78. As shown in FIG. 13, theoperation vehicle 10 and the marker 71 can be connected by a line frompositions 10-A, 10-B, 10-E, and 10-F without an interference with theobstacle 78. On the other hand, as shown in FIG. 13, the operationvehicle 10 and the marker 71 cannot be connected by a line frompositions 10-C and 10-D without an interference with the obstacle 78.

That is, for example, while the operation vehicle 10 is moving in themoving direction shown in FIG. 13 while capturing the outside by thecamera 21, a situation (lost) in which the marker 71 extracted by theimage analysis unit 43 from images captured at the positions 10-A and10-B cannot be extracted by the image analysis unit 43 from an imagecaptured at the position 10-C occurs. After that, when the operationvehicle 10 moves up to the position 10-E, the image analysis unit 43 canextract the marker 71 from a captured image again, and the lost iseliminated.

For example, if no measure is taken, the image analysis unit 43 isassumed to recognize the marker 71 extracted before the occurrence ofthe lost and the marker 71 extracted after the lost is eliminated asdifferent markers 71. For example, if such a lost occurs during the timewhen the operation vehicle 10 moves to cause the survey unit 45 toacquire the position information of the marker 71, the survey unit 45 isassumed to be unable to accurately acquire the position information ofthe marker 71 or unable to acquire the position information of themarker 71. That is, information used by the survey unit 45 to acquirethe position information of the marker 71 is limited to one ofinformation (the marker detection angle and the marker detectionposition) obtained before the operation vehicle 10 reaches the position10-C (before the occurrence of the lost) and information (the markerdetection angle and the marker detection position) obtained after theoperation vehicle 10 reaches the position 10-E (after the elimination ofthe lost).

For example, according to the flowchart of FIG. 12, step S211 ends withNO, or step S206 ends with NO. For example, if step S211 ends with NO,the second angle and the second point stored during the time when theoperation vehicle 10 moves to the position 10-C are determined as thesecond angle and the second point to be used in triangulation (stepS214), and the position information of the marker 71 is obtained bytriangulation using them together with the already determined firstangle and first point (step S215). In this case, there is a possibilitythat the position information of the marker 71 cannot accurately beacquired. If step S206 ends with NO, the procedure ends withoutacquiring the position information of the marker 71.

In the example shown in FIG. 13, when the operation vehicle 10 moves upto the position 10-E, the image analysis unit 43 can extract the marker71 from a captured image again. Hence, the image analysis unit 43 maydetermine whether the marker 71 extracted before the occurrence of thelost and the marker 71 extracted after the elimination of the lost arethe same marker 71. If the marker 71 extracted by the image analysisunit 43 before the occurrence of the lost and the marker 71 extractedafter the elimination of the lost are the same marker 71, the surveyunit 45 may acquire the position information of the marker 71 using boththe information (the marker detection angle and the marker detectionposition) obtained before the occurrence of the lost and the information(the marker detection angle and the marker detection position) obtainedafter the elimination of the lost.

Then, as compared to a case in which the survey unit 45 acquires theposition information of the marker 71 using only one of the informationobtained before the occurrence of the lost and the information obtainedafter the elimination of the lost, the position information of themarker 71 can accurately be acquired. In addition, for example, duringthe movement of the operation vehicle 10, the user need not guide theoperation vehicle 10 up to a position without an influence of theobstacle 78.

An example of a method of allowing the image analysis unit 43 todetermine whether the marker 71 extracted after the elimination of thelost and the marker 71 extracted before the occurrence of the lost arethe same marker 71 if the lost occurs and is eliminated will bedescribed with reference to FIGS. 14A to 14D.

As an example of an image captured by the camera 21 before theoccurrence of the lost, FIG. 14A shows an image 80B captured at theposition 10-B in the example of FIG. 13. As an example of an imagecaptured by the camera 21 after the elimination of the lost, FIG. 14Bshows an image 80E captured at the position 10-E in the example of FIG.13. FIG. 14C shows a processed image 80Bi as an example of an image forwhich the image analysis unit 43 has performed image processing ofremoving elements other than the marker 71 from the image 80B. FIG. 14Dshows a processed image 80Ei as an example of an image for which theimage analysis unit 43 has performed image processing of removingelements other than the marker 71 from the image 80E. Note that FIGS.14A to 14D do not illustrate the obstacle 78.

As an example of the method, the image analysis unit 43 may compare theshape feature of the landscape near the marker 71 on the image 80B withthe shape feature of the landscape near the marker 71 on the image 80E.The image analysis unit 43 may determine based on the comparison resultwhether the marker 71 included in the image 80B and the marker 71included in the image 80E are the same marker 71. According to thisexample of the method, the shape feature of the landscape near themarker 71 can be used for the determination. This is effective when, forexample, a characteristic object (for example, a tree) is included inthe landscape near the marker 71. This method also provides the effectof guaranteeing the accuracy of determination even in a case in which itis difficult to determine the matching using only the shape feature ofthe marker 71, for example, in a case in which an image captured afterthe elimination of the lost includes a plurality of markers 71 havingthe same shape.

As another example of the method, the image analysis unit 43 may predicta position where the marker 71 included in the image 80B is included inthe image 80E using the distance between the position 10-B in theexample of FIG. 13 and the position 10-E in the example of FIG. 13 andcompare the predicted position of the marker 71 on the image 80E withthe actual position of the marker 71 on the image 80E. The imageanalysis unit 43 may determine based on the comparison result whetherthe marker 71 included in the image 80B and the marker 71 included inthe image 80E are the same marker 71. According to this example of themethod, the distance of the movement of the operation vehicle 10 can beused for the determination. This method provides the effect ofguaranteeing the accuracy of determination even in a case in which it isdifficult to determine the matching using only the shape feature of themarker 71, for example, in a case in which an image captured after theelimination of the lost includes a plurality of markers 71 having thesame shape.

As still another example of the method, the image analysis unit 43 maycompare the shape feature of the marker 71 on the processed image 80Biwith the shape feature of the marker 71 on the processed image 80Ei. Theimage analysis unit 43 may determine based on the comparison resultwhether the marker 71 included in the image 80B and the marker 71included in the image 80E are the same marker 71. According to thisexample of the method, the shape feature of the marker 71 can be usedfor the determination. This is particularly effective when, for example,the marker 71 has a characteristic shape.

As yet another example of the method, the image analysis unit 43 maypredict a position where the marker 71 included in the processed image80Bi is included in the processed image 80Ei using the distance betweenthe position 10-B in the example of FIG. 13 and the position 10-E in theexample of FIG. 13 and compare the predicted position of the marker 71on the processed image 80Ei with the actual position of the marker 71 onthe processed image 80Ei. The image analysis unit 43 may determine basedon the comparison result whether the marker 71 included in the image 80Band the marker 71 included in the image 80E are the same marker 71.According to this example of the method, the distance of the movement ofthe operation vehicle 10 can be used for the determination. This methodprovides the effect of guaranteeing the accuracy of determination evenin a case in which it is difficult to determine the matching using onlythe shape feature of the marker 71, for example, in a case in which animage captured after the elimination of the lost includes a plurality ofmarkers 71 having the same shape.

Several examples of the method of allowing the image analysis unit 43 todetermine whether the marker 71 extracted after the elimination of thelost and the marker 71 extracted before the occurrence of the lost arethe same marker 71 if the lost occurs and is eliminated have beendescribed. The image analysis unit 43 may make a determination using aresult obtained by solely executing one of the methods, or may make ageneral determination using a result obtained by executing two or moreof the methods. The image analysis unit 43 may execute a method otherthan those described above and make a general determination inconsideration of the result as well.

Not all the operations of the operation vehicle 10 described above needbe executed. That is, the operation vehicle 10 may execute part of theexamples of the operation described above.

The present invention is not limited to the above-described exemplaryembodiments, and those skilled in the art can easily change theabove-described exemplary embodiments within the range included in thescope of the appended claims.

A first aspect according to the present invention is directed to anautomatic operation vehicle that automatically performs an operation inan operation area, comprising:

a behavior acquisition unit configured to acquire behavior informationincluding a distance of a movement of the automatic operation vehicleand a direction of the movement;

an image analysis unit configured to extract a marker included in animage captured by a camera provided on the automatic operation vehicle;and

a survey unit configured to acquire, by triangulation, positioninformation of the marker extracted by the image analysis unit,

wherein the survey unit acquires the position information of the markerusing a first angle that is an angle difference between the movingdirection and a direction to the marker from a first point through whichthe automatic operation vehicle passes during the movement in a constantmoving direction, a second angle that is an angle difference between themoving direction and a direction to the marker from a second pointthrough which the automatic operation vehicle passes during the movementin the moving direction, and a distance between the first point and thesecond point, the second point being different from the first point, and

the survey unit determines the first point and/or the second pointduring the movement of the automatic operation vehicle in the movingdirection such that the angle difference between the first angle and thesecond angle becomes close to 90°.

Generally, in a camera capable of generating an image of a digitalformat, when forming an image of an object on the imaging plane of animage sensor, an error occurs because of the resolution of the imagesensor, the focal length of the imaging lens, and the like. The surveyunit determines the first point and/or the second point during themovement of the automatic operation vehicle in the constant movingdirection such that the angle difference between the first angle and thesecond angle becomes close to 90°, thereby reducing the influence of theerror. As a result, the user need not determine the first point and thesecond point to guarantee the accuracy of the acquisition of theposition information of the marker.

In a second aspect according to the present invention, in addition tothe first aspect, during the movement of the automatic operation vehiclein the moving direction, the survey unit may determine the first pointsuch that the first angle becomes close to 45°, and may determine thesecond point such that the second angle becomes close to 135°.

The influence of the error becomes large as the distance between thecamera and the marker increases. In the second aspect, the survey unitcan shorten both the distance between the first point and the marker andthe distance between the second point and the marker.

In a third aspect according to the present invention, in addition to thefirst or second aspect, during the movement of the automatic operationvehicle in the moving direction, if the angle difference between themoving direction and the direction from the current position of theautomatic operation vehicle to the marker is closer to 45° than thefirst angle at the already determined first point, the survey unit maydetermine the current position as the first point in place of thealready determined first point, and if the angle difference between themoving direction and the direction from the current position of theautomatic operation vehicle to the marker is not closer to 45° than thefirst angle at the already determined first point, the survey unit mayuse the first angle at the already determined first point to acquire theposition information of the marker.

In the third aspect, during the movement of the automatic operationvehicle in the moving direction, the first point can be determined suchthat the first angle becomes close to 45°.

In a fourth aspect according to the present invention, in addition toany one of the first to third aspects, during the movement of theautomatic operation vehicle in the moving direction, if the angledifference between the moving direction and the direction from thecurrent position of the automatic operation vehicle to the marker iscloser to 135° than the second angle at the already determined secondpoint, the survey unit may determine the current position as the secondpoint in place of the already determined second point, and if the angledifference between the moving direction and the direction from thecurrent position of the automatic operation vehicle to the marker is notcloser to 135° than the second angle at the already determined secondpoint, the survey unit may use the second angle at the alreadydetermined second point to acquire the position information of themarker.

In the fourth aspect, during the movement of the automatic operationvehicle in the moving direction, the second point can be determined suchthat the second angle becomes close to 135°.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2016-055478, filed Mar. 18, 2016, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. An automatic operation vehicle that automaticallyperforms an operation in an operation area, the vehicle comprising: abehavior acquisition unit configured to acquire behavior informationincluding a distance of a movement of the automatic operation vehicleand a direction of the movement; an image analysis unit configured toextract a marker included in an image captured by a camera provided onthe automatic operation vehicle; and a survey unit configured toacquire, by triangulation, position information of the marker extractedby the image analysis unit, wherein the survey unit acquires theposition information of the marker using a first angle that is an angledifference between the moving direction and a direction to the markerfrom a first point through which the automatic operation vehicle passesduring the movement in a constant moving direction, a second angle thatis an angle difference between the moving direction and a direction tothe marker from a second point through which the automatic operationvehicle passes during the movement in the moving direction, and adistance between the first point and the second point, the second pointbeing different from the first point, and the survey unit determines thefirst point and/or the second point during the movement of the automaticoperation vehicle in the moving direction such that the angle differencebetween the first angle and the second angle becomes close to 90°. 2.The vehicle according to claim 1, wherein during the movement of theautomatic operation vehicle in the moving direction, the survey unitdetermines the first point such that the first angle becomes close to45°, and determines the second point such that the second angle becomesclose to 135°.
 3. The vehicle according to claim 1, wherein during themovement of the automatic operation vehicle in the moving direction, ifthe angle difference between the moving direction and the direction fromthe current position of the automatic operation vehicle to the marker iscloser to 45° than the first angle at the already determined firstpoint, the survey unit determines the current position as the firstpoint in place of the already determined first point, and if the angledifference between the moving direction and the direction from thecurrent position of the automatic operation vehicle to the marker is notcloser to 45° than the first angle at the already determined firstpoint, the survey unit uses the first angle at the already determinedfirst point to acquire the position information of the marker.
 4. Thevehicle according to claim 1, wherein during the movement of theautomatic operation vehicle in the moving direction, if the angledifference between the moving direction and the direction from thecurrent position of the automatic operation vehicle to the marker iscloser to 135° than the second angle at the already determined secondpoint, the survey unit determines the current position as the secondpoint in place of the already determined second point, and if the angledifference between the moving direction and the direction from thecurrent position of the automatic operation vehicle to the marker is notcloser to 135° than the second angle at the already determined secondpoint, the survey unit uses the second angle at the already determinedsecond point to acquire the position information of the marker.
 5. Amethod of controlling an automatic operation vehicle that automaticallyperforms an operation in an operation area, the method comprising:acquiring behavior information including a distance of a movement of theautomatic operation vehicle and a direction of the movement; extractinga marker included in an image captured by a camera provided on theautomatic operation vehicle; and acquiring, by triangulation, positioninformation of the extracted marker, wherein the acquiring the positioninformation includes: acquiring the position information of the markerusing a first angle that is an angle difference between the movingdirection and a direction to the marker from a first point through whichthe automatic operation vehicle passes during the movement in a constantmoving direction, a second angle that is an angle difference between themoving direction and a direction to the marker from a second pointthrough which the automatic operation vehicle passes during the movementin the moving direction, and a distance between the first point and thesecond point, the second point being different from the first point, anddetermining the first point and/or the second point during the movementof the automatic operation vehicle in the moving direction such that theangle difference between the first angle and the second angle becomesclose to 90°.
 6. An automatic operation vehicle that automaticallyperforms an operation in an operation area, the vehicle comprising: oneor more processors; memory; and one or more programs stored in thememory and configured to be executed by the one or more processors, theprograms including instructions for: acquiring behavior informationincluding a distance of a movement of the automatic operation vehicleand a direction of the movement; extracting a marker included in animage captured by a camera provided on the automatic operation vehicle;and acquiring, by triangulation, position information of the extractedmarker, wherein the acquiring the position information includes:acquiring the position information of the marker using a first anglethat is an angle difference between the moving direction and a directionto the marker from a first point through which the automatic operationvehicle passes during the movement in a constant moving direction, asecond angle that is an angle difference between the moving directionand a direction to the marker from a second point through which theautomatic operation vehicle passes during the movement in the movingdirection, and a distance between the first point and the second point,the second point being different from the first point, and determiningthe first point and/or the second point during the movement of theautomatic operation vehicle in the moving direction such that the angledifference between the first angle and the second angle becomes close to90°.
 7. A non-transitory computer readable medium storing a programcausing an automatic operation vehicle that automatically performs anoperation in an operation area, to execute a process, the processcomprising: acquiring behavior information including a distance of amovement of the automatic operation vehicle and a direction of themovement; extracting a marker included in an image captured by a cameraprovided on the automatic operation vehicle; and acquiring, bytriangulation, position information of the extracted marker, wherein theacquiring the position information includes: acquiring the positioninformation of the marker using a first angle that is an angledifference between the moving direction and a direction to the markerfrom a first point through which the automatic operation vehicle passesduring the movement in a constant moving direction, a second angle thatis an angle difference between the moving direction and a direction tothe marker from a second point through which the automatic operationvehicle passes during the movement in the moving direction, and adistance between the first point and the second point, the second pointbeing different from the first point, and determining the first pointand/or the second point during the movement of the automatic operationvehicle in the moving direction such that the angle difference betweenthe first angle and the second angle becomes close to 90°.